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Lough Derg concern over alien invasion

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AN ALIEN invasion is underway in Lough Derg causing concern for the local ecosystem.
The alien in question is a mussel called the guagga, originally from Ukraine, which has been found in the lake by a local marine biologist.
The guagga mussel was found in early July in Ireland. A team from UCD, led by Dr Jan Robert Baars, discovered its presence in large numbers in Lough Ree.
Lower numbers were found downstream in Lough Derg by Dr Dan Minchin of the Lough Derg Science Group, where it is expected its numbers will increase.
Dr Minchin has been working on projects with Dr Baars on the River Shannon since 2016.
This species, Dreissena rostriformis bugensis, known as the quagga mussel, is expected to expand and suppress the numbers of the closely-related zebra mussel that arrived in Ireland in 1994.
It is thought the zebra mussel arrived as fouling on imported leisure craft ferried from the Midlands of Britain.
It is not known how the quagga mussel arrived in Ireland, but it may also have been with fouled craft. The zebra mussel looks very similar to the invader, with which it can be easily confused.
The quagga mussel is an aggressive invader. In other areas in Europe and in North America where it was introduced, it appears to have a preference for cooler water conditions, explaining its occurrence in deeper water.
This mussel is also capable of spawning over a wider range of temperatures than the zebra mussel, which increases the risk of the fouling of pipework used for abstracting water.
The climatic conditions in Ireland are suitable for this new species to expand further. While currently restricted from Lough Ree southwards in the Shannon River, it is expected to spread to the northern Shannon, and through the Shannon-Erne Waterway to the Erne, through the fouling on boats.
It is also expected to spread to other water bodies with the overland transmission of trailered boats, as has already happened with the spread of the zebra mussel.
There are no known practical ways of eliminating either the quagga or zebra mussel, except using local treatment methods and practices preventing it from spreading elsewhere.
Anyone moving boats from the Shannon should be aware that they could spread this species.
Dr Minchin recalled the first time he came across this quagga mussel was during a study in lower Lough Derg with Paul Murphy, of EirEco based in Carron, and his team who were involved in a diving study.
He discovered some white mussels that proved to be quagga mussels in a dredge sample, which he had never seen before in the middle of the river off the Lakeside Hotel this June 28.
Within days, he sampled about the edge of the lake at some selected marina sites from Terryglass to the Parteen Dam and found low numbers.
However, Dr Minchin stressed this may not represent the real levels in the lake, because this species has been recorded elsewhere with a preference for deeper water.
It is believed these mussels may have arrived before 2019.
To date, in Lough Derg he has not found the quagga mussel on boat hulls. He suspects that there will be a further development of this species not unlike the zebra mussel with an increase in its abundance, and perhaps a fouling like they have experienced at one time with the zebra mussel.
“There is no doubt we are having to experience the impacts of a further species which is likely to result in a greater biomass in the deeper waters of Lough Derg.
“Should this happen, as with the reported ability of the quagga mussel to settle and grow on siltier sediments in the deeper water, there could be a problem.
“There is a possibility of the deeper and cooler water, in a prolonged hot windless period as can happen in summer, that the water in the lower levels of the lake could become oxygen depleted.
“It is a possible scenario with consequences to a wide die-off of bottom living organisms.
“This is yet a further impacting species that can modify water quality, have impacts on native species and through its fouling ability result in economic costs.”

by Dan Danaher

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